1. Field of the Invention.
The present invention relates to semiconductor radiation emitting devices. In particular, the present invention relates to a semiconductor device which produces radiation based on radiative recombination of electrons from a two-dimensional electron gas with holes from a two-dimensional hole gas induced in the semiconductor device.
2. Description of the Prior Art.
Light emitting diodes and semiconductor lasers are widely used to produce radiation, particularly in the infrared and some portions of the visible part of the electromagnetic spectrum. A light emitting diode makes use of a semiconductor PN junction which is forward biased to emit spontaneous radiation. This radiation is produced by the radiative recombination of holes and electrons within the semiconductor material. The particular wavelength at which the semiconductor device emits depends upon the energy band gap of the semiconductor material, and whether the material is a direct or indirect band gap material.
Semiconductor lasers are semiconductor PN junction devices which produce radiation which has spatial and temporal coherence. Selected surfaces of the semiconductor laser are polished, and appropriate dimensions are selected so that the semiconductor device becomes an optical resonator.
There have been continuing research efforts expended on the development of light emitting diodes and lasers using semiconductor materials having energy gaps compatible with the shorter wavelength portions of the visible spectrum, the UV spectrum and beyond. The development of light emitting diodes and semiconductor lasers in these portions of the spectrum, however, has trailed the development of devices in the infrared and longer wavelength visible spectrum because of numerous problems with the semiconductor materials themselves. One problem is the tendency of wider band gap materials to be non-amphoteric (i.e. the materials can only be impurity doped one conductivity type). For example, zinc selenide can be doped N-type but P-type doping is extremely difficult. Other materials have, to date, been capable of impurity doping in only one conductivity type. This, of course, has in the past precluded the use of those materials as a PN junction light emitting diode or semiconductor laser.
In addition, the use of impurity doping in order to produce PN junctions creates traps in the device which permit non-radiative recombination. This decreases the amount of radiation which can be emitted, and thus decreases the efficiency of the device and limits its output power.